Printing telegraph system utilizing variably spaced impulses



Oct. 2s,-1947.. J. J. B. LAIR 2,429,632

PRINTING TELEGRAPH SYSTEM UTILIZING VARIABLY SPACED IMPULSES Filed Jufip22,1945 4 Sheets-Sheet 1 v I a v 50 511 52 v 1- z 5 4 g K I 6 6bczdafmjbwp 6 m FH(T(T T(H INVENTOR.

JUL/EN J. B. LA/l? Oct. 28, 1947. J,- J, B. LAIR 2,429,632

PRINTING TELEGRAPH SYSTEM UTILIZING VARIABLY SPACED IMPULSES Filed June22, 194; 4 Sheets-Sheet 2 (7 r 'ciaA. 0 l it i i E I I i a I" 3 6; i l t5O 51 WWW k T T T T T ,7 r cw 1 INVENTOR.

JUL/EN J B. um?

Oct.28, 1947. 'J,J B,LA|R 2,429,632

PRINTING TELEGRAPH SYSTEM UTILIZING VARIABLY SPACED IMPULSES Filed June22, 1943 4 SheerQs-Sheet s I V1100 102 7r 2 Q 11w 5 ,7 7 INIV/ENTOR.

W I v JULY/EN J 5. mm BY 1 1 W AGENT Oct. 28, 1947. J, 2,429,632

PRINTING TELEGRAPH SYSTEM UTILIZING \ARIABLY SPACED IMPULSES Filed June22, 1945 4 Sheets-Sheet 4 121 l 1 (EL-I 162 Ill (1| 111 2 v I IINVENTOR. JUL/EN I B. LA/R Patented Oct. 28, 1947 PRINTING TELEGRAPHSYSTEM UTILIZING VARIABLY SPACED IIVIPULSES Julien J. B. Lair, Paris,France, assignor to International Standard Electric Corporation,

New

York, N. Y., a corporation of Delaware Application June 22, 1943, SerialNo. 491,804

In France Septe 12. Claims. (01. 17868) The present invention, which isa continuationin-part of application Ser. No. 488,300, filed May 24,1943, relates to printing telegraph instruments and particularly toprinting telegraph instruments for use in systems in which thetransmitted signals are characterized by three currents or lineconditions, namely a positive current, a negative current and. a zerocurrent, and are sent in the form of impulses displaced or staggered intime. Each letter, figure or symbol to be transmitted and printedaccordingly is characterized by the relative staggerings in time withrespect to a time origin, of a special combination of impulses, i. e. byan impulse modulation.

These systems generally use electromechanical devices both at thesending and the receiving ends for selecting the desired characters.These electromechanical devices are usually rather com plicated and donot allow the sending of messages at a very high transmission speed.

One of the objects of the present invention is consequently theproviding of printing telegraph transmitters that are free from thesedrawbacks owing to the fact thatthey do not re.- quire anyelectromechanical selecting device.

According to certain features of the invention, use is made in printingtelegraph transmitters of the three current or line conditions type(positive current, negative current and no current) of a pulse generatorin association with an artificial line that terminates at itscharacteristic impedance and is disposed so as to furnish theparticularimpulses that correspond to the predetermined code of signals under thecontrol of an automatic or manual manipulating device (e. g. a key setor a perforated tape).

The pulse generator sends its pulses simultaneously into thetransmission line that leads to the remote receiver and into theartificial .line. When there is no manipulation, the pulses directedinto the artificial line are absorbed without reflection by thecharacteristic impedance that terminates it. When there is manipulation,this line is opened or short-circuited at particular points thatcorrespond to the characters to be transmitted; the pulses are thenreflected into this line and, upon leaving the line, are directed to thetransmission line where their time displacements from the directlytransmitted pulses and their polarity (positive or negative) define atthe reception end the characters they represent.

According to one feature of the invention, the direction'of thereflected pulses is obtained by making use of the following property ofartificial mber 12, 1941 2 lines: When a pulse of a certain polarity issent into the line and is reflected in it by an interruption of the linedue to an opening of the circuit, the reflected pulse upon returning tothe input of the line will be of the same polarity as the incomingpulse; inversely, if the interruption of .the line is due to ashort-circuit, the reflected pulse upon returning to the input of theline will be of opposite polarity to that of the incoming pulse. In thisway, a reflected positive pulse will be obtained either by sending apositive pulse into the artificial line and causing its reflection bymeans of an opening of the line, or by sending a nega tive pulse intothe line and causing its reflection by a short-circuit of the line.Inversely, a reflected negative pulse will be obtained either by sendinga negative pulse into the line and cans ing its reflection by means ofan opening of the; line, or by sending a positive pulse into the lineand causing its reflection by means of a short-circuit of the line.

According to other features of the invention, the retarded pulsesareobta'ined without reflection in the artificial line, and simply bymaking use of their time-lag in propagation over this line as far as thepoints that correspond to the desired characters, where they are shuntedto the transmission line that leads to the receiver. In this case, thepolarities of these pulses will be determined in the pulse generatoritself which is of such a type as to furnish either positive or negativepulses as desired, by control of the manipulation. I

These features, as well as others, are explained in detail in thefollowing description given with reference to the appended drawings, inwhich:

Fig. 1 illustrates schematically one example of a printing telegraphtransmitter according to the invention which employs a pulse generatorthat generates pulses of a definite polarity, and an artificial linedisposed so as to provide pulses of definite time-lag and of positive ornegative polarity according to the Figs. 2A and 2B show graphs relatingto the device of Fig. 1;

Figs. 3A and 3B show graphs in which the directions of the pulses aredetermined by the pulse generator itself;

Fig. 4. illustrates schematically one example of a pulse generator thatemits either positive or negative pulses as required;

Fig. 5 illustrates a variant of the pulse generator circuit of Fig. 4;

Fig. 6 is a schematic view of one example of a printing telegraphtransmitter according to the transmitted characters;

invention, using a pulse generator of the kind shown in Figs. 4 and 5,and a staggering of the impulses by reflection;

Fig. 7 illustrates schematically one example of a printing telegraphtransmitter according to the invention; using. a pulse generator of thekind shown in Figs; 4' and 5, and a staggering of the pulses bypropagation;

Figs. 8A to 8D show graphs relating to the operation of a printingtelegraph transmitter similar to the one shown in Fig. 1. but using apulse generator of the kind shown in Figs. l and Fig. 9 illustrates amodification or the circuit shown in Fig. 6 which furnishes positive andnegative pulses, but which uses a pulse: generator that furnishes onlyunidirectional pulses.

First referring to Fig. 1, the device illustrated in this drawingcomprises a generator I which generates pulses of a definite polarity,as indicated by the and signs at its output terminals. The pulsesproceeding from the generator I are sent to the transmission line 3 thatleads to the remote receiver or receivers, and also to an artificialline designated in its iretyby the reference number 2.

In the example of an embodiment shown in the drawin'gathis artificialline 2 consists of a series of T'-shaped impedance sections comprisinginductance units L1, L2, L3, etc., and capacity units C1, C2, G3, etc.,although it may be made up of any suitable type of sections, e. g. of 1ror lattice shape. The total number of sections depends upon the numberof characters to be transmitted; In this. arrangement there are half asmany impedance sections as there are characters in the code to betransmitted and printed and each section. has a series switch 50', 51,52, etc. capable of" opening and closing the artificial line at therespective sections, and a series of shunt switches Bil, BI, 62, etc.capable of short-circuiting the line at the respective sections. Theline terminates at its characteristic impedance 6, so as to absorbwithout reflection. any pulses. fromthe generator I. when all the seriesswitches 56', El, 52, etc. are closed and all the shunt switches 60, 61,62;. etc. arev open, this being the normal condition. of. the line whenthere is no signalling or manipulation. The first letters of thealphabet to which these switches are assigned are indicated' alongsidethem, (a, c, e, for the series switches 5U, 51', 52 and b, d, for theshunt switches 6B, 6!, 62.- The condition of the series and shuntswitches when there is no manipulation consequently insures that theartificial line 2. will have a condition of continuity between its inputterminals and its terminal impedance 6, and also that it will not beshort-circuited at any point. While in this condition, if the generatorI periodically emits pulses to the transmission line 3 and to theartificial line 2, no pulse. that comes. intoline 2 will be reflected tothe transmission line 3-, and only the directly transmitted pulses willbe propagated to the remote receiver.

When signalling, hereinafter termed manipulation takes place, eithermanually, e. g. by means of a key set (not shown), or automatically, e.g. from a, suitable recorder, one of the switches 50, etc. or 69', etc.that corresponds to the desired character is opened or closed. The pulseemitted at this moment by the generator I (which may be controlledsolely by a manipulation effected by a switch located in the circuitinstead of having, to emit continuous periodic pulses) is reflected backalong the artificial line 2 from the location of the switch that hasjust been opened or closed by the manipulator.

If the closed switch is one of the switches of the 50, 5|, etc. series,in other words, if a discontinuity has been created in the artificialline 2,.the-.reflectedpulse will be of the same polarity or direction asthe incoming pulse, and consequently as the pulse sent directly into thetransmission line 3. The stagger of the two pulses, direct andreflected, of the same polarity on the transmission line 3 willcharacterize the transmitted signal. If the closed switch be the shuntswitchof the same numerical order in the line, the reflected pulse willhave on the transmission line 3 the same stagger as the direct pulse,but since. the artificial line 2 has in this instancezbe'enshort-circuited rather than opencircuited at the location of thisswitch, the polarity of the reflected pulse will be the reverse of thatof the direct pulse, and this additional characteristic will defineadifferent signal.

It is consequently evident that with an artificia-l line of this kindthere is constituted a telegraph transmitting system employing two typesof currents in which the number of sections of the artificial line ishalf the number of characters (letters, figures and symbols) to betransmitted.

The pulse generator i may be of any well known or suitable design.Furthermore, a line amplifier may, if desired, be inserted at thecommencement of the transmission line 3 in order tocompensate for theattenuation undergone by the reflected pulses in the artificial line 2.This amplifier should preferably be provided with means fordiscriminating between the direct pulses and the reflected pulses (e. g.by only being sensitive to one impulse out of each two consecutivepulses in. order effectively to amplify only the reflected pulses.

The graphs of the line transmission pulses will accordingly be like thatshown as an example in. Figs. 2A and 2B. In Fig. 2A, which correspondsto an opening of the switch representing the letter e, the direct pulseis indicated at 10. The pulse reflected by opening of the switch 52 isindicated at H and is of the same direction as the direct pulse. In Fig.2B, which corresponds to closure of switch 62, representing the letterI, the direct pulse is still designated by the reference number it. Thepulse reflected by the closing, of switch 62 is indicated at 12, and ithas the same spacing with respect to the pulse 10 as the pulse 1 I ofFig. 2A, but is of reverse polarity.

Instead of providing a mode of transmission in which. the original pulseremains of the same sign, while two diiTerent signals with componentpulses of equal stagger are distinguished by their identical or reversepolarity with respect to said original. pulse, it is also possible,according to the invention, to provide a method of transmission in whichthe pulse generator I can furnish positive or negative pulses asdesired, the reflected pulses being of the same polarity as the originalpulses. One half of the signals can then be transmitted with thepositive pulses, and the other half with the negative pulses.

In this case, the graphs of the pulses received over line 3 will be asshown in Figs. 3A and 3B. When the pulse generator I emits a positivepulse 73 (Fig. 3A), the reflected pulse M will still be of the samepolarity, i. e. positive, and its stagger will characterize thetransmitted signal. When the pulse generator emits a negative pulse 15(Fig. 3B), the reflected pulse 16 will still be of the same polarity, i.e. negative, and its stagger will characterize the transmitted signal.Two different signals having a same spacing T between the constituentpulses will accordingly be characterized by the polarity of both of thetwo pulses of which they consist. It will accordingly be sufiicient inthis case to provide an artificial line which has a number of sectionsthat is half the number of the signs or letters to be transmitted andwhich is equipped with a series of series switches, the opening of whichlatter will cause the reflection of pulses of the same polarity as theincoming pulses. It is evident that use may be made of an artificialline equipped with shunt switches. In this case, the refiected pulsewould always have a polarity the reverse of that of the direct pulse.The receivers used with these transmitters will consequently have to bearranged to discriminate between the polarities of the pulses and to besensitive either to two pulses of the same polarity or to two pulses ofopposite polarities while at the same time discriminating the polarityof the first pulse.

Figs. 4 and 5 illustrate schematically two embodiments of single pulsegenerators that furnish either positive or negative pulses under controlof the manipulation. In the circuit of Fig. 4, two batteries 18 and IIor other sources of direct current, deliver to self-inductance coils 80and 8I, respectively, currents that are adjustable by resistances I8 andI9. Condensers 84 and 85 prevent direct current from flowing in theartificial or phantom line and in the transmission line associated withthis generator. The output of the two circuits of the batteries 16 and11 may be tapped across a common resistance 86.

When, for example, one of the switches of the artificial line (accordingto the arrangement of the switches) is opened or closed by depressing akey of the signalling key assembly, either switch 82 or switch 83 isopened by the same mechanical control. Assuming that switch 82 has beenopened, the current from battery I6 will be cut off. There is thenproduced at the terminals of inductance coil 80 an extra current surgeor kick that furnishes a pulse, the brevity of duration of which dependsessentially on the rapidity of interruption, and on the value ofinductance 88 and of the time constant of the self inductanceresistanceimpedance formed by this inductance coil 80. Condenser 84, which is oflow capacity, permits passage of the steep front of the positive pulsewhich is generated in this way and the duration of which can easily bereduced to values of the order of a microsecond.

.The operation of the circuit of battery 11 will be similar when switch83 is opened. However, a negative pulse will then be obtained on accountof the reverse polarity of the battery connections with respect to theother elementsof the circuit.

In the schematic view of the pulse generator shown in Fig. 5, condensers88 and 89 are charged slowly by batteries 16 and 11 (since switches 82and 83 are open) across adjustable resistances I8 and 19. In contrast tothe pulse generator of Fig. 4, an impulse is generated by the closing ofswitches 82 or 83, one of which causes the rapid discharge of condenser88 or 89 through resistance 88. A positive pulseis obtained by closingswitch 82 and a negative pulse by closing switch 83 on account of thereversed connection of batteries 16 and I! in their respective circuits.

Figs. 6 and '7 illustrate two examples of telegraph transmitters whichemploy pulse generators that furnish at will either positivepulsesor'negative pulses, such as those shown in Figs. 4 and 5.

In the arrangement shown schematically in Fig. 6, the positive andnegative pulse generator I sends pulses simultaneously into thetransmission line 3 and into the artificial or phantom line 2 theswitches 50, 5I, etc. of which are, for example, disposed in series inthe line so as to 'cause pulse reflections when they are opened. Thesignalling or manipulation is effected by opening simultaneously any oneof the switches 58 and either one of the switches 82 and 83 of the pulsegenerator. The opening of the switch 82 or 83 determines the sending ofeither a positive or a negative pulse, and the opening of one of theswitches 58, 5|, etc. determines the stagger between the direct andreflected pulses transmitted to the remote receiver or receivers.

Instead of employing a staggering of pulses by reflection, it ispossible, according to another embodiment of the invention, to produceproper staggering by simple propagation into the artificial line 2. Fig.7 illustrates an example of the use of this feature, using a generatorproducing either positive or negative pulses, at will. In the form ofFig. 7, generator I sends impulses into phantom line 2, each switch 98,9|, 92, etc. of the artificial line 2 serves for withdrawing pulses atthe points where each switch is located, every time that a switch isclosed. The manually or automatically controlled signalling ormanipulation mechanism simultaneously closes one of the switches 90, 9 Ietc, and either switch 82 or switch 83' of generator I, so that a pulseof desired polarity is generated and transmitted along phantom line 2 asfar as the switch closed.

The direct pulse from generator I is transmitted to the control grid ofa tube I88 the load impedance of which is indicated at I02 and the anodecircuit of which is connected to the transmission line 3 via condenserI04, in order to avoid applying the high anode voltage to this line 3.The pulse retarded by line 2 is transmitted by one of the switches 98,8|, 92, etc. to the control grid of another tube II the load impedanceof which is indicated at I83 and the anode circuit of which is similarlyconnected to the transmission line 3 via a condenser I85, used forblocking the flow of direct current. The common source of anode feed isindicated at I88. It should be noted that tube's'lilfi and IIJI shouldnot be adjusted at their cut-off point because they have to amplifyeither positive or negative pulses. Their biasing is accordinglyadjusted by means of resistances I88 and I89. The pulses are applied tothe control grids of tubes I08 and IIlI via condensers H8 and III, whichlatter are of sufficiently low capacity to prevent the signallingmanipulation from causin'g any appreciable accidental surges reachingthe line.

Another modification of the telegraph transmitter which incorporatesfeatures of the invention includes the use of a pulse generator that canfurnish either positive or negative pulses as desired with the type ofartificial line illustrated in Fig. 1, i. e. one that can furnish byreflection either positive return pulses or negative return pulses. Inthis case, the artificial line requires only half the elements orsections necessary in the case of Fig. 1 for transmitting the samenumber of signals.

The graphs of pulses received over line 3 will then be as shown in Figs.8A to 8D in the case of the letters a, b, c and d, for example. When thesignalling manipulation closes switch 5!! (Fig. 1) and switch 82 of Fig.5 or opens switch 82 of Fig. 4, the letter ais transmitted to thereceiver in the form of the pulses M2 and I I3 of Fig. 8A. These twopulses are of the same polarity and are spaced apart by an interval T.

When the manipulation closes switch 68 (Fig. 1) and switch 82 of Fig. ,5(or opens switch 82 of Fig. 4), the letter b is sent over the line 3 inthe form of the pulses H2 and I! (Fig. 8b) These two pulses are ofopposite polarity and are spaced apart by an interval T of the samevalue as for letter a.

When the manipulation closes switch 50 (Fig. 1) and switch 83 of Fig. 5(or opens switch 83 of Fig. l), the letter is sent over the line 3 inthe form of the pulses H and H6 (Fig. 80). These two pulses are of thesame polarity but the opposite of that of the pulses IIZ and H3 (Fig.8A) and their distance apart is still T.

When the manipulation closes switch 60 (Fig. 1) :and switch '83 of Fig.5 (or opens switch 83 of Fig. 4)., the letter d is sent over the line 3in the form of the pulses H5 and II! (Fig. 8D). These two pulses are ofdifferent polarity, the first one being negative, and their stagger ordistance apart is still T.

It can consequently be seen that a single timelag section of theartificial line 2 is sufficient for sending four distinct characters.The number of sections of the artificial line will accordingly be onefourth of the total number of characters to be transmitted.

Instead of using two impulse generating circuits side by side as shownin Figs. 4 and 5 for obtaining either positive or negative impulses,another embodiment of the invention provides for the use of a singlegenerating circuit in association with switching means that reverses thetwo output terminals of the pulse generator. This reversing means has tobe controlled in synchronism with the manipulation device that is used.The order in which the various switchings has to be made is accordinglyas follows:

By pressing on the key that corresponds to a figure or a letter, theoutput reversingimeans of the pulse generator is placed in the necessaryposition (positive or negative pulse). By continuing to press, theartificial line 2 is opened (or short-circuited) at the desiredlocation. At the end of its travel, the manipulation key releases theemission of the pulse. Such a sequence of operations, which may beeffected in' any well known mechanical or electromechanical manner,takes place in a very short time, so that the operations may be said tobe substantially synchronous.

It is quite evident that this is very important because it defines aregularity in the operations to be effected, such regularity beingindispensable for the proper operation of the instrument.

The transmitter arrangement illustrated schematically in Fig. 9,according to the invention, provides a means for obtaining positive andnegative pulses by only using a simple pulse generator employing onlythe upper or the lower half of the circuit of the types shown in Fig. 4or Fig. In this arrangement, the graphs of the line signals are similarto those shown in Figs. 8A to 8D. In other words, a single section ofthe timelag line is sufiicient for obtaining four desired differentcharacters, depending on the manipulation.

The pulse generator i feeds into a resistance I26. A mid-tap I2! of thisresistance permits the obtaining of positive pulses between the pointsIZI and 52-2, and negative pulses between the points I21 and I23. Thesepulses are sent over an artificial line 2 of the symmetrical or balancedtype, 'as shown by way of example, and it is accordingly possible todeliver either positive pulses by the switches I39, I3I, etc. ornegative pulses by the switches I MI, MI, etc.

The artificial line can furnish positive 'or negati-ve pulses, but it isalso necessary to be able to send the time origin pulse as a positive ornegative pulse. This is accomplished by means of a switch I6I whichconnects the control grid of tube 13!] either to terminal IZ'Z orterminal I23 of the output resistance .I'Zll of the pulse generator I,while the cathodes of tubes *Iilfi and I 01 are connected to themid-point I'2I of this resistance by a connection I62. The mean biasvalue of tubes I50 and 'IIII is determined by the resistances Hi8 andH39. Battery I06 feeds the tube anodes through'resistors I 02 and IE3,respectively, and the anodes are coupled to output 3L via condensers I64and N15.

The manipulation will be efiected as in the preceding cases, i. e. the:pulse will be released by the pulse generator after the setting inposit-ionof switch 'IiiI and one of the switches I30 or Mil, dependingon the character that is to be transmitted. For transmission of theletter a, for example, switch I30 will be closed and switch iiiI willconnect the terminal I22 of resistance I-Eil to the control grid of tubeHill. The pulse will be released by the generator and this will causethe sending into the line of the two impulses that "define the letter a.by their direction and time displacement. The direct pulse travels fromgenerator I, via points I 22, NH, tube iiiil and condenser IM to line3L. The retarded pulse travels via I22, line -2, switch I-SU, couplingcondenser III, tube IiII and condenser I05 to line 3L. For transmissionof the letter I), switch Hill will also be closed, but switch I'GI willbe brought into the position in which it connects the terminal I23 ofresistance I'2il to the control grid of tube Itt. Similarly, the letters0 and it will be sent by the closing of switch Mil. It can consequentlybe seen that the first symmetrical section of the artificial linepermits the sending of four signals, and similarly for all the othersections of line 2'.

The transmission speed of these devices depends on the duration of theimpulses and also on the 'length (in time-lags) of the artificial line.The transmission time in the artificial line is dependent upon thenumber of sections, i. e. the

ignated by 0, for the purpose of selecting signals that correspond totwo adjacent sections of the artificial line, the shortest distance intime that can be practically used is equal to 0. In order to insuregreater certainty of operation, it is possible and suitable to make thisdistance equal to 1.5 0 or more according to the nature of thetransmission line with which the device is associated.

If, for example, we take a time 6 equal to -2 microseconds and 20sections for 40 signs to be transmitted (Fig. 1), the length of theartificial line will be from 40 to 60 microseconds depending uponwhether the stagger time per cell is taken to be equal to 0 or to 1.5 0.

It is evident that a signal can be sent only when there has elapsed atime equal to the transfer time after the emission oi-a pulse. I Asubsequent signal can therefore only be transmitted 40 to 6 microsecondsafter the sending of a preceding signal, and this permits the sending ofabout 10,000 to 15,000 signals per second. Such a speed may be utilizedin the case of automatic signalling manipulation over a perforated orrecording tape, since the transmission takes place automatically.

In the case of an artificial line that permits the sending of foursignals per section instead of two, the above figures'will have to bedoubled.

For simple instruments, pulses of greater widths will have to be used.It is evident however, in the case of direct manipulation by theoperator, that there is no risk of his jumbling the signals by too rapidmanipulation, irrespective of the speed with which he strikes the keys.

The transmission speed of the device under consideration also depends onthe maximum recording speed of the associated receiver or receivers. Inthe case of ordinary types of receivers, it will be necessary to useimpulses of longer duration and artificial lines that provide a greaterstagger or displacement of the pulses.

The invention makes it possible in every case to use the time intervalsavailable between two consecutive signals for placing the transmissionline at the disposition of one or more other operators, in other wordsto effect multiple transmissions by means of pulses of short duration.

It will be noted that circuit arrangements have been provided wherebytwo or more pairs of pulses are produced which have the same staggerrelation but difier in their polarity to provide two difierent signals..It is immaterial whether the generator or generator means generatesimpulses of two polarities and the switching means inthe artificial linedevelops a delayed pulse of the same polarity or the generating meansgenerates a pulse of a single polarity and the switching means for theartificial line produces a delayed pulse of two different polarities. Ineither case a series of two pairs of pulses may be produced having thesame stagger relation but difierent polarities namely two pulses of thesame polarity and two pulses of opposite polarity but with the samestagger relation if the generating means provides pulses of difierentpolarities or'two pulses of the same polarity (positive or negative) andtwo pulses of opposite polarity but with the same stagger relation ifthe switching means is utilized to develop the signals. In a circuit inwhich both the generator means and the switching means produce pulses ofopposite polarity then a series of four pulse signals may be transmittedeach having the same stagger relation but differing in polarity namelytwo positive pulses, two negative pulses, a positive primary pulse and anegative secondary or delayed pulse and lastly a negative primary pulseand a positive secondary or delayed pulse, each of which may be used asa separate distinct signal.

Although the invention means of certain particular examples orembodiments, it is evident that it is by no means lim ited thereto buton the contrary is capable of numerous modifications, and adaptationswithin the scope of the following claims.

Having described my invention, I claim:

1. A printing telegraph system of the type in which the characters to betransmitted are translated into signals consisting of pulses spaced bydifierent time staggers, comprising a pulse generator generating pulsesof definite polarity, a

has been described by I neously and selectively controllabletransmission line receiving pulses of constant polarity directly fromsaid generator, an artificial line connected to said generator andhaving a plurality of impedance sections producing retardations in thepulses it receives erator said artificial line being arranged to reflectthese pulses into said transmission line with different time staggersrelatively to said directly received pulses, means in each impedancesection for opening and closing the artificial line thereat, and meansin each impedance section for making and breaking a short-circuit of theartificial line thereat, both said means being selectively operable inthe course of signalling to vary the polarity of the staggered pulses ofa signal reflected into said transmitting line whereby the transmittedsignal is defined by the stagger in combination with the polarity of itscomponent pulses.

2. A printing telegraph system of the type in I which the characters tobe transmitted are translated into signals consisting of pulses spacedby different time staggers, comprising a pulse generator generatingpulses of both polarities, a transmission line receiving said pulsesdirectly from said generator, an artificial line also connected to saidgenerator and having a plurality of impedance sections producingretardations in the pulses it receives from said generator saidartificial line including a plurality of switches operable so as toreflect these pulses into said transmission line with different timestaggers relatively tosaid directly received pulses, there being aswitch in each impedance section for rendering it operable andinoperable to so reflect pulses, said switches and said pulse generatorbeing simultain the course of signalling to vary the polarity of thepulses delivered to said transmission and artificial lines by saidgenerator whereby the transmitted signal is defined by the stagger incombination with the polarity of the component pulses from theartificial line.

. 3. A printing telegraph system of the type in which'the haracters tobe transmitted are translated into signals consisting of pulses spacedby different time staggers, comprising a pulse generator' generatingpulses of both polarities, a transmission line receiving said pulsesdirectly from said generator, an artificial line also connected to saidgenerator and having a plurality of impedance sections producingretardations in the pulses it receives from said generator saidartificial line being provided with a plurality of switches controllingdirect propagation of these pulses and their delivery with stagger tosaid transmission line relatively to said directly received pulses,there being a switch in each impedance section and movable for renderingthe section operable and inoperable to so reflect pulses, said switchesand said pulse generator being simultaneously and selectivelycontrollable in the course of signalling to vary the polarity of thepulses delivered to said transmission and artificial lines by saidgenerator whereby the transmitted signal is defined by the stagger incombination with the polarity of the component pulses from theartificial line.

4. A printing telegraph system of the type in which the characters to betransmitted are translated into signals consisting of pulses spaced bydifierent time staggers, comprising a pulse generator, a transmissionline receiving pulses directly from said generator, an artificial lineconnected to said generator and a movable control from said genswitch,in each section, andhaving a plurality of impedance sections producingretardations in the pulses it receives from said generator saidartificial line being arranged to introduce its pulses into saidtransmission line with different time staggers depending on the switchpositions, relatively to said directly received pulses, and means forchanging the polarity of said pulses in the course of signalling wherebythe transmitted signal is, defined by the stagger in combination withthe polarity of the component pulses from the artificial line.

5. In a system according to claim 2, a generator yielding positive andnegative pulses including two sources of direct current connected atopposite poles, two induction coils energized respectively by saidsources, a. switch between the positive pole of one source and itsinduction coil; a switch between the negative pole of the other sourceand its induction coil, a connection between said switches, aresistancetapped across the junction of said sources and saidlconnectionsaid resistance feeding the output of the generator to the transmissionline and artificial lines, and condensersblocking flow of direct currentinto said lines, said switches being. operable in the course ofsignalling.

6. In a system according to claim 2 a generator yielding positive andnegative pulses including two sources of direct current connected atopposite poles, a pair of condensers arranged to be charged at apredetermined rate by said sources, a connection between saidcondensers, two switches connected one to discharge pulses from thepositive terminal of one source andthe other to discharge pulses fromthe negative terminal of the other source, and meansfor introducing suchpositive and negative pulses into said transmission and artificial linessaid switches. being operable in the course of signalling.

7. A printing telegraph system of the type in V which the characters tob transmitted are trans.- lated into signals consisting of pulses spacedby diiferent time staggers, comprising a pulse generator generatingpulses of definite polarity, a transmission line receiving pulses of:constant polarity directly from saidgenerator, an artificial'lineconnected to saidgeneratorv and having a plurality ofimpedancesectionsproducing re-. tardations in the pulses it receivesfrom said generator said artificialline being arranged to introducethese pulses into said transmission line with different time staggersrelatively to said directly received pulses, means in eachirnpedancesection for opening and closing the artificial line thereat, and meansin each impedance section for making and breaking a short-circuit of theartificial line thereat, both said means being selectively operable inthe course of signallingto vary the polarity of the staggeredpulsesof asignal introduced into said transmitting line whereby the transmittedsignal is definedloyv the stagger in combination with the polarityof-its component pulses.

8. A printing telegraph system; of the type in which the characters tobe transmitted are translated into signals consisting of pulses spacedby difierent time staggers, comprising apulse generator generatingpulses of both polarities, a transmission line recei g a d uu ses r yfrom said generator, an artificial, line also connected to saidgenerator and having a; plurality ofimpedance sections, each-with acontrol switch therein, for selectively producing retardations inthepulses it receives fromsaid generator said artificial line beingarranged to introduce these pulses into said transmission line withdifierent time staggers dependent upon switch position relatively tosaid directly received pulses, the switch in each impedance sectionrendering it operable and inoperable to so introduce pulses, saidswitches and said pulse generator being simultaneously and selectivelycontrollable in the course of signalling to vary the polarity of; thepulses delivered to said transmission and artificial lines by saidgenerator whereby the transmitted signal is defined by; the stagger incombination with the polarity of; the component pulses from theartificial line,

9. In a signalling system, in; combination, a pulse generator forgenerating, pulses, of either polarity, a transmission line, anartificial line, a circuit connecting the two lines in parallel to thegenerator, a plurality of impedance sections in the artificial line eachcomprising, a condenser connected across the line. and an inductance inseries in the line, a switch'in series with each inductance and movableto open or close the line at a point just beyond its inductance wherebyto cause a pulse in the artificial linetobe reflected back into thetransmission line fromthe place of the first open switch, andwithno-change in polarity, whereby simultaneousandselective operation of thegenerator and a. switch. results in a pair of selectively spaced pulses,of, like polarity being transmitted by the transmission line.

10. In a signalling system, thecombination of a pulse generatorgenerating pulses of at. least, one polarity, a transmission lineconnection to receive pulses directly fromsaid generator; an artificialline having a length proportional to the number of pulse polarities.generated and such that separate pulses result including aplurality ofseries impedance sections and a, plurality of. shunt impedance elementsconstituting a plurality of impedance sections, a seriesswitchforeachsection of said artificial line, and ashunt switch for each sectionof. said artificial'line, said'arti" ficial line being-connected withthe transmission line connection to receive pulses from the generatorand to reflect. the pulsestherefrominto said transmission lineconnection atdifferent time intervals following thereceiptofepulseshfrom said generator; and means for selectively.operating said series and shunt switches to determine the length of theartificial line andrthe stagger interval between the primary pulse andthe reflected pulse and the polarity of the reflectedpulsa 11. In asignalling system, thecombination of a pulse generator generating pulsesof at, least one polarity, a transmission line connection to receivepulses directly from-said generator; an artificial line having alengthproportional to the number of pulse polarities generated. and suchthat separate pulses result including a plurality of series impedancesections and a plurality of shunt impedance elements constituting a plurality of impedance sections, a normally closed series switch foreachsectionof saidartificial line, and a normally open shunt switch foreach section of said artificial line, said-artificial linebeingconnected with the, transmission line con-. nection to receivepulses fromthegenerator and to reflect the pulses therefrom; into.said'transmission line connection at-differenttime intervals followingthe reoeiptof pulsesfrom saidgenerator; and -rn eansiorselectiyelyoperating said series. and, shunt switches to;determine-the length of the artificial line andthe. staggerinterval :be

tween the primary pulse and the reflected pulse and the polarity of thereflected pulse.

12. In a signalling system, the combination of a pulse generating meansfor generating pulses of at least one polarity, a transmission lineconnection to receive pulses directly from said generating means, anartificial line having a length proportional to the number of pulsepolarities generated and such that separate pulses result including aplurality of impedance sections and at least one movable switch means ineach section, said artificial line being connected to the transmissionline connection to receive pulses from said generating means, the switchmeans being positionable for controlling said artificial line totransmit delayed pulses therefrom into said transmission line connectionat different time intervals following the receipt of pulses from saidgenerating means, operating mechanism for selectively operating saidswitching means, and at least one of said means producing pulses ofopposite polarity whereby both the stagger interval between the primarypulse and the delayed pulse and the polarity of the pulses may beselected.

JULIE N J. B. LAIR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number

